Apparatus for producing an absorbent element for filters



Nov. 12, 1957 R- M HENRY APPARATUS FOR PRODUCING AN ABSORBENT ELEMENT FOR FILTERS Filed April 13, 1955 United States Patent R APPARATUS FOR PRODUCING AN ABSORBENT ELEMENT FOR FILTERS Richard MacHenry, Prospect Park, Pa., assignor to Amen ican Viscose Corporation, Philadelphia, Pa., :1 corporation of Delaware Application April 18, 1955, Serial No. 501,894

14 Claims. cl. 1s4-1.7

The present invention relates to an apparatus for producing fibrous elements which are highly porous and exhibit good liquid or moisture retention properties. Specifically the invention relates to an apparatus for producing fibrous tobacco smoke filter material. However, the absorbent fibrous elements may be used in dental or surgical pads, dressings, tampons and the like.

Tobacco smoke is made up of a mixture of gaseous compounds and finely divided solids. The smoke comprises tar, phenol, acetic acid, acrolein, carbon dioxide, water vapor, and solid dust particles. These compounds and elements are formed and derived from the disintegration of the tobacco and in the case of cigarettes, the cigarette paper wrapper. Most of these substances are contained in tobacco smoke in the vapor state. The tobacco smoke filters in use today trap only minor portions of these ingredients of tobacco smoke as mentioned above. The major portions of these ingredients are not trapped by the fibrous filters and they pass through the filter into the smokers mouth and lungs. These tobacco smoke filters have not proved to be entirely satisfactory and the tobacco companies, especially the cigarette manufacturers, are constantly searching for improved tobacco smoke filters.

The requirements for a satisfactory tobacco smoke filter are, first, that it effectively remove toxic or harmful ingredients from the smoke drawn into the users mouth. Secondly, the filter must be sufficiently porous so that it does not interfere with free passage of the smoke or what is commonly termed the draw. In addition, a cigarette filter must be suificiently firm to support the cigarette without bending or becoming undesirably soft and flabby. It will be appreciated from the above requirements that good draw is ordinarily inversely proportional to filtering ability, namely, the denser the filter, the more effective is the filtering, but suction required to draw the smoke through the filter is also higher. Due to the peculiar beneficial structure resulting from a uniform mixture of a major proportion of crimped staple fibers and a minor proportion of potentially adhesive fibers which serve to bond the mixture together, I have been able to produce a filter which approaches the desired results of maximum filtering combined with easy draw.

It is an object of my invention to provide an apparatus which is simple in construction for producing an absorbent fibrous element of high porosity.

Another object of my invention is to provide an apparatus for producing an internally bound, firm bodied, absorbent element for medical and surgical uses.

Another object of my invention is to provide an apparatus which is simple in construction for producing tobacco smoke filter material having good draw properties, sutficient density and stifiness.

It is a further object of my invention to provide in an apparatus for producing my fibrous element from a mixture of potentially adhesive and non-adhesive fibers, a chamber through which a sliver or bundle of the poten tially adhesive fibers and non-adhesive crimped textile Patented Nov. 12, 1957 fibers are passed wherein the potentially adhesive fibers are activated to autogenously bond together the non-adhesive and adhesive fibers.

It is still a further object of my invention to provide in the activating chamber of the above object means for introducing an activating agent for the adhesive fibers into the chamber.

It is still a further object of my invention to provide an apparatus for producing tobacco smoke filters from a sliver of potentially adhesive and non-adhesive fibers which apparatus includes a chamber through which the sliver is drawn and wherein the adhesive fibers within the sliver are activated to autogenously bond together the fibers within the sliver, and means for wrapping the sliver in a paper wrapper after the sliver has emerged from the chamber.

Another object of my invention to provide in the activating chamber of the above object means for releasing excess vaporized activating agent from the chamber.

A final object of my invention is to provide in an activating chamber for activating the potentially adhesive fibers within the sliver passing through the chamber, a novel type inlet or entrance die for the sliver passing into the chamber which die substantially eliminates any activated fiber build up on the die.

Other objects and advantages will become more apparent from a study of the following description and drawing in which:

Figure l is a perspective of my fibrous element in bundle or sliver form;

Figure 2 is a perspective of my tobacco smoke filter;

Figure 3 is a perspective of a filter type cigarette with my tobacco smoke filter incorporated therein;

Figure 4 is a side partially sectioned view of the apparatus for forming my filter; and

Figure 5 is an enlarged fragmentary view taken along lines V-V of Figure 4.

Briefly my apparatus for producing my fibrous absorbent element and my tobacco smoke filter plugs from nonadhesive fibers and potentially adhesive fibers comprises an elongated chamber through which a sliver formed from a m1xture of above fibers is drawn and wherein the potentially adhesive fibers are activated as the sliver passes therethrough. The chamber is heated by a series of heating umts secured to the chamber wall. Means extending through the chamber wall is provided for introducing therewithin an activating agent for the potentially adhesive fibers. An entrance die for feeding the sliver into the chamber extends through an end wall of the chamber and an exit die through which the sliver is discharged from the chamber extends through the opposite end wall of the chamber. The exit die is of a smaller bore than the entrance die whereby the activated sliver is condensed as it leaves the chamber. The entrance die has a novel construction whereby any build-up of activated fibers is substantially eliminated at its exit end. Means is provided for further compressing and wrapping the sliver with a paper cover after it leaves the chamber.

It will be understood that throughout the following specification and claims, the terms non-adhesive and potentially adhesive refer to types of fibers, one of which becomes tacky or adhesive under conditions under which the other fiber is relatively unaffected. Where the tacky or adhesive condition results from elevated temperature, the potentially adhesive fibers will, of course, be of a thermoplastic nature. Ordinarily, the non-adhesive fiber will not be thermoplastic but a thermoplastic fiber could be used provided the temperature at which it became tacky is sufiiciently higher than the temperature at which the other potentially adhesive fiber becomes tacky. By way of example, the potentially adhesive fibers are formed from vinyl resins resulting from the polymerization of compounds containing the vinyl group such as polyvinylchloride or copolymers of vinyl chloride and vinyl acetate. Other potentially adhesive fibers, however, may be used successfully in the present invention, for example, certain copolymers of vinyl chloride and acrylonitrile.

Referring now to the drawings wherein preferred embodiments of my invention are shown, Figure 1 shows the fibrous element in bundle or sliver form. As seen therein the sliver A is a carefully blended mixture of nonadhesive regenerated cellulose fibers, such as rayon staple, and potentially adhesive or thermoplastic fibers. The fibers mentioned above are of the textile fiber class having diameters of at least 9 microns.

The mixture of the present invention can be satisfactorily formed by uniformly distributing 10-25% of the potentially adhesive fibers into the major proportion, 75 90% by weight, of crimped rayon staple fiber.- It has been found that the potentially adhesive fibers should comprise at least 10% by weight of the mixture and preferably should be in the range of 10-15% by weight.

The length of the individual fibers, both potentially adhesive and non-adhesive, may vary from A2 to 2 /2 inches and should be between 1 to 2 /2 denier, preferably 1 to 1 /2 denier. Due to the crimp in the non-adhesive fibers and, if desired, in the potentially adhesive fibers, minute traps or voids are formed within the body of the element which enhance the absorptiveness of the element and also provide for the porosity which in turn permits easy draw.

The fibers specified above range in weight from l00-125 grains and the fine relatively short length fibers provide a compact, dense structure in which many of the shorter length fibers will lie across the general longitudinal axis of the element.

An important feature of my invention is that the nonadhesive or rayon fibers within the fibrous mass are crimped. In the case of rayon, the fibers may be crimped chemically as distinguished from a mechanical crimp. Such chemical crimping is disclosed and claimed in United States Patent 2,517,694. This crimping remains in the fiber even when it is wet. The filaments, however, may be mechanically crimped according to well known processes and apparatus. Since relatively small denier fibers are used to form the element and since the fibers are crimped, numerous minute traps or voids are formed within the element which render the fibrous element capable of entrapping and retaining liquids, moisture and minute solid particles. The potentially adhesive fibers may or may not be crimped. When converting the fibrous sliver to specific articles of use, the potentially adhesive fibers are activated, as will be explained hereinafter, to autogenously bond together the non-adhesive fibers in the sliver A. The fibers are compressed, as will also be explained, after the potentially adhesive fibers have been activated to provide a compact article of good strength.

A tobacco smoke filter or plug B formed from the fibrous mass or sliver A of Figure 1 is shown in Figure 2 of the drawing. The tobacco smoke filter B, in this instance, is of cylindrical shape. The potentially adhesive fibers have been activated and compressed to autogenously bond together the non-adhesive rayon fibers and the potentially adhesive fibers to provide a compact cylindrical shaped article of good strength. When the completed element is to be used as a cigarette filter, the bonded element is wrapped or stuffed in a paper wrapper 2 and cut into suitable lengths to form the filter plug B.

Figure 3 shows the wrapped filter plug B of Figure 2 incorporated in a cigarette C. The tobacco and the filter plug B are formed into a unitary cigarette having the usual cigarette paper Ill.

The apparatus for forming and converting the mixed sliver to a tow or rod from which filter elements can be cut has been designed to insure a combination of all the desired properties for a cigarette filter. Such a filter element must have firmness or body, maximum filtering ability, and porosity to permit free and easy draw. As is well known in the filter art, density of the filter is inversely proportional to the draw or pressure required to force the fiuid through the filter. In the present filter and ap paratus it has been possible to obtain maximum filtering and absorbing properties without increasing the density to the point where there is an objectional lack of draw. The crimped fibers which are autogenously bonded into a uniform element with the minor proportion of either crimped or uncrimped potentially adhesive fibers cooperate to provide this unexpected and desired result.

The apparatus in which the relatively loose sliver is activated and transformed into a comparatively strong, dense but porous rod comprises a chamber or tube 18 into which the sliver 19 is drawn through a funnel shaped die 2% mounted in the forward end wall 21 of the chamber. The tacky sliver is drawn out of the chamber 18 through a relatively longer die 23 mounted in the rear wall 24 of the chamber and in alignment with die 20. Die 23 has a sub stantially smaller bore than entrance die 20. The preferred diameters for the entrance and exit dies are and /8 of an inch respectively when it is desired to fabricate a cigarette filter. For other articles the dimension of the bores may be changed but substantially the same ratio should be maintained. The inside of the chamber 18 is maintained at an elevated temperature of approximately C. by means of one or more heating elements 25, 25 which surround the walls of the chamber. if desired, the heating elements are covered by suitable insulating material 27 through which electrical connections to the heaters may be made at 28, 28. At a point approximately midway between the downstream terminus of die 25 and the upstream terminus of die 23 a liquid softening or activating agent such as acetone is introduced to the chamber through a nozzle 3%. The acetone may fall directly on the sliver in the chamber or it may be vaporized when it falls onto the heated chamber wall. in either event the potentially adhesve fibers in the sliver are sufficiently softened throughout the sliver so that when the sliver is drawn through die 23 there is a compression or rearrangement of the structure to provide a firm, compact, internally bound but porous rod 31. The potentially adhesive fibers set up after leaving die 23 when they are cooled and the acetone evaporates or is otherwise removed. Partial setting up may take place in the bore of die 23 and the length and relative axial position of this forming die in the end wall 24 is so controlled to provide the results which may be desired. in order to eliminate sticking or deposition of material in the bore of either of the dies, they are preferably made of polytetrafiuoroethylene, sold commercially under the trade name of Teflon.

Depending upon the degree of activation found desirable and the speed with which the sliver is drawn through chamber 18 by means of draw rolls R, R, it may be found necessary or desirable to provide limited venting for the chamber. This can be accomplished by the provision of one or more flats 35, 35 (Figure 5) along the side of the entrance die 26. These flats extend through the end wall 21 so that limited venting of the interior of chamber 18 is achieved.

By providing an annular bevel 40 on the downstream end of die 24 it is possible to prevent build-up or adherence of fibers 'to any part of die 20.

When the activated sliver is to be used for tobacco smoke filters, the rod 31 passes through a wrapping upparatus 50 wherein a continuous sheet of wrapping paper 55 supplied from a reel 56 is folded around the rod. The wrapper 55 is sealed by applying an adhesive from a liquid adhesive applicator 60 connected with an adhesive supply container 61. The diameter of the bore of the wrapping apparatus 50 through which the activated tow passes is somewhat smaller than the diameter of the exit die 23 of the activation chamber or pipe 18 whereby the diameter of the tow is further reduced to correspond with the diameter of a cigarette or tobacco cylinder with which the filter plug B is to be incorporated.

V aporizcd acetone as an activating agent for the potentially adhesive fibers is preferred in that it has been found that the fibers within the tow which have been subjected to vaporized acetone are more firmly bound together and the finished filter plug exhibits greater stiffness and excellent draw which features also contribute to the success of the filter. It has also been found that the cleaner cuts may be made with the acetone activated filter plug. in the apparatus described above, the softening of the potentially adhesive fibers is achieved primarily by means of the solvent, namely, acetone, which is applied to the fibers. However, it will be understood that the temperature in chamber 18 may be sufiiciently elevated to assist or, if desired, completely provide for the softening of the minor proportion fibers.

Another important feature or" my invention is that the filtering efficiency of a tobacco smoke filter improves during use. An inherent property of viscose rayon is that it swells considerably when in contact with water or moisture. When my filter is incorporated with a cigarette, the filtering action improves as the tobacco cylinder burns down since the rayon fibers swell when contacted by the moisture carried by the smoke. The smoke components or ingredients which have been filtered out by the base portion of the tobacco cylinder will therefore be more effectively filtered out by the swollen fibers as the base portion of the tobacco cylinder burns.

Various colored fibers may be used in the filter to pro vide a variety of color schemes for the filter. The dye pigment matter may be incorporated with the filament forming spinning solution. Undyed extruded filaments, from which the staple is cut, may be dyed by passing the filaments through suitable dye baths.

If desired, aromatics such as perfume or menthol may be incorporated with the filter material to provide a filter having a pleasing arc-ma. In addition, other desired or essential oils may be incorporated with the filter.

My tobacco smoke filter plug is porous and has excellent draw properties which permits the smoker to easily pull the smoke through the filter. The filter is economical to produce and has sufficient strength and firmness to permit normal processing of the filter when incorporating it with cigarettes or other tobacco smoking article.;. As explained above, the filter plug contains many minute voids or traps because fine denier fibers are used and because the fibers contain a crimp. The traps easily catch and retain the vapor and solid components of the smoke passing therethrough.

As mentioned above, my fibrous element has numerous uses since it has good li aid and moisture retention properties. Among the uses other than for tobacco filter material is that of dental saliva pads which are placed within the patients mouth to absorb excess saliva. Tanipons may also be produced from my fibrous absorption mass. The fibrous mass may also be used in other fields of medicine and surgery wherein liquid retentive pads are required.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

I claim:

1. Extrusion apparatus for fibrous material comprising an elongated and substantially enclosed forming chamber, means for heating the interior of the chamber, an entrance die in one end of the chamber, an exit die in the opposite end of the chamber, said exit die having 'a smaller bore than the entrance die, and a conduit leading into the chamber for introducing a fluid into said chamber.

2. Extrusion apparatus in accordance with claim I having a vent for the chamber adjacent the entrance die.

3. Extrusion apparatus in accordance with claim I in which the ratio of the diameter of the bores of the dies is approximately 2: 1.

4. Extrusion apparatus in accordance with claim 1 in which the fluid-introducing means is positioned intermediate of the entrance and exit dies.

5. Apparatus in accordance with claim 1 in which the exit die is substantially longer than the entrance die and extends into the chamber.

6. Apparatus for continuously softening and forming a running sliver of staple fibers comprising an elongated and substantially enclosed forming chamber, a sliver entrance die at one end of said chamber, means for heating the interior of said chamber, means for introducing a liquid softening agent for the fibers into the chamber, and a siiver exit die of substantially smaller bore than the entrance die at the opposite end of the chamber.

7. Extrusion apparatus in accordance with claim 6 having a vent for the chamber adjacent the entrance die.

8. Extrusion apparatus in accordance with claim 6 in which the ratio of the diameter of the bores of the dies is approximately 2: 1.

9. Extrusion apparatus in accordance with claim 6 in which the fluid-introducing means is positioned intermediate of the entrance die and the exit die.

10. Apparatus in accordance with claim 6 in which the exit die is substantially longer than the entrance die and extends into the chamber.

11. An apparatus for producing an elongated fibrous rod of crimped potentially adhesive fibers and non-adhesive fibers comprising an elongated walled chamber wherein the potentially adhesive fibers are activated, end closures for the walled chamber, means secured to the chamber wall for heating the chamber wall and chamber interior, an entrance die for the fiber mixture extending through one end closure for the chamber, and an exit die for the fiber mixture extending through the opposite end closure for the chamber, the bore of said exit die being smaller than that of the entrance die.

12. An apparatus according to claim 11 in which the bore of the entrance die is A of an inch in diameter, and the bore of the exit die is of /8 of an inch in diameter.

13. An apparatus for producing a continuous sliver of crimped potentially adhesive fibers and non-adhesive fibers comprising an elongated walled chamber through which a sliver of the fiber mixture is passed and wherein the potentially adhesive fibers are activated, end closures for the chamber, electrically heated plates secured to the chamber wall for heating the chamber wall and the chamber interior, a conduit extending through the chamber wall for introducing an activating agent for the potentially adhesive fibers, an entrance die for the sliver extending through one end closure of the chamber, flat surfaces on the periphery of said die whereby excess activating agent may escape from the chamber, and an exit die for the sliver extending through the opposite end closure of the chamber, said exit die having a smaller bore than the entrance die.

14. An apparatus according to claim 13 having a sharp beveled edge on the downstream end of the entrance die.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,675 Lang July 20, 1948 2,483,406 Francis Oct. 4, 1949 2,684,318 Meek July 20, 1954 2,773,179 Smith Ian. 31, 1956 OTHER REFERENCES Article entitled: New High Temperature Thermoplastic, appearing in Modern Plastics, October 19, 1948; pages 168, and 172 of interest. 

